Determining the state of our health has always been a matter of finding a way to monitor and measure the body’s most basic functions. Before instrumentation, visual indicators were used that allowed us to know, for example, what our body temperature should be, what a healthy pulse is, and what an acceptable respiration rate is.
Today, with an aging population more people now need some sort of portable health monitoring, which could take the form of devices that, among other things, dispense medication at regular intervals, stimulate the heart, or measure blood sugar levels and inject insulin. This article looks at medical- and fitness-sensor technology—contacted and contact-less, placed on the skin, subcutaneous, or internal—that now or soon will be available to design engineers. All parts, tools, and data referenced here can be found on the Digi-Key website.
Simple beginnings
The simplest form of a sensor is a transducer, which can be as basic as two different substances touching each other. The actual sensor element can be fabbed as a small discrete leaded component, or as part of a probe or electrode assembly. They can be as thin as a hair-like wire and can actually generate voltages themselves. Thermocouples are an example of voltage-generating sensor of dissimilar metals that creates voltages based on temperatures. Parts like the non-grounded Omron E52-CA15AYD32 4M, for example, measure temperatures using a K-type element with a 3.2 mm protective tube capable of skin mount or mounting in a stationary crevice.
Piezo effects can be taken advantage of to create energy from a tiny embeddable sensor when exposed to shock and vibration. A small, rather non-intrusive skeletal sensor could indicate too much physical trauma to a football player in real time to avert more serious injury. The miniaturizing of piezo sensors means they can now be weaved into textiles, bandages, or clothing. Sheet sensors like the TE Connectivity 2-1004347-0 are flexible, foldable, and can be cut to very specific states (Figure 1). A shoe insert for example, could determine if too much stress is being generated on downward steps to help diagnose back or joint issues.
This is just one example of how transducers integrated with system electronics can result in small and compact medical devices that are not very intrusive. Weaving sensors into textiles can be used as a way of monitoring a physiological condition without surgery or without the need to carry around medical boxes. One such technology is in the form of smart socks where the textiles are infused with stress sensors and can track steps, speed, calories, and distance. However, they do more. These socks can also detect altitude so oxygen levels can be adjusted depending on the available oxygen density.
For more detail: Sensor Technology for Health and Fitness Applications
